Definitely continue your SAT preparation. Get a good night’s sleep the night before the SAT. When taking the SAT do not get too hung up on any one question. There will be at least a few questions on the SAT which are intentionally really hard.
Once you have your real SAT results you will be in better shape to predict your chances at highly selective schools.
And… relax. Your good grades in school will get you into a very good university, even if it is not in the Ivy League.